The present invention relates to a plastic manifold for hot-water heating systems and the like.
In the prior art manifolds are made of metal and are cast or made by drawing and additional operations. Such manifolds are used not only in the circuits of heating systems using radiators but also in heating systems using floor or wall-mounted coils or radiant panels, which can also be used to cool rooms during summer months, by using cold water. The main disadvantage of metal manifolds consists in their use in the latter category of systems: circulation of a fluid at a temperature lower than the ambient temperature inevitably leads to condensation on the outer surface of the manifolds. In turn, this condensation causes infiltration of damp patches on the walls or on the floor where the manifold assemblies are fitted or embedded. In addition, the use of metal material and the need for special operations mean that this type of manifold involves considerable costs.
In order to reduce condensation and, as a secondary benefit, to reduce the cost of these products, manifolds have recently been proposed made of batteries of modular elements moulded in plastics material working this type of material is definitely less expensive, while the better insulating properties of plastics materials significantly reduce the problem of condensation.
In order better to understand the art and the problems inherent thereto, a description is first provided of modular units of a known type, with reference to FIGS. 1 and 2 of the appended drawings.
The modular units of the type illustrated in FIGS. 1 and 2 include a main body 1 in the shape of a sleeve open at each end, having a generally horizontal axis and forming internally a tubular diametral portion 2. The bottom end of the tubular portion 2 is fitted to a threaded pipe coupling 3 for connection to a pipe, indicated T of a secondary circuit; a seat 4 for a valve, indicated 5 and 6 respectively in FIGS. 1 and 2, is formed in the upper end of the tubular portion. The internal opening 7 of the tubular portion is in communication with the cavity of the main body and is shaped in such a way that fluid coming from the manifold, if the unit is a delivery one (FIG. 1) or from a secondary circuit if the unit is a return one (FIG. 2) flows first through the seat 4 of the valve. Both types of modular unit are constituted by a single piece of moulded plastics material, except for the pipe coupling 3 which is made of metal, generally brass, which is embedded in the plastics material at the time of the moulding operation, with a ribbed root portion 8.
The individual units are mounted in succession along the axis y, with O-ring type sealing elements 9 mounted between the modules to ensure they are fluid tight. These units make up horizontal batteries which act as water delivery or return manifolds and, as individual units, as flow dividers for the secondary circuits connected to them. In delivery manifolds having units of the type shown in FIG. 1, water enters the battery at one end and leaves through the pipe couplings to supply the various branches of the heating system. The circuit of each individual branch can be excluded from the water circulation by means of respective shut-off valves 5. In return manifolds, on the other hand, which are composed of units of the type shown in FIG. 2, the water returns from the various branches of the system through the pipe couplings of the respective modular units and flows out through one end of the battery. The flow through the individual circuits is regulated by respective regulator valves 6. Brackets then secure the batteries, as part of a modular assembly, to a support structure fixed to a wall.
The modular arrangement of the manifold assemblies provides flexibility in use and makes it possible to absorb the overall heat expansion of the batteries at the interface of the individual modules, since the O-ring seals are able to deform and still ensure a hydraulic seal.
The main disadvantage of the modular arrangement consists in the possibility of leaks in the connection portions between modules and the consequent need for complicated and expensive maintenance. Another disadvantage, connected on the other hand to the construction methods of the individual modules, consists in the fact that inevitable variations in cyclical heat expansion, due to the different heat expansion coefficients of plastics materials and metal, can cause detachments at the interface of the plastic body and the ribs of the metal pipe couplings, which then lead to fluid leakage. In such an event it is necessary to replace the module.